I want to use a new selective neurotoxic tool to examine a question with basic neurobiological significance to a wide range of areas, including early development, aging, and recovery of function. A variety of developmental studies have suggested that there may be a relationship between neuronal death and dendritic extent of remaining neurons. The influence of partial, experimentally produced loss of alpha retinal ganglion cells on plasticity (growth) of dendritic trees of the remaining, neighboring population of alpha cells will be examined. The selective, partial loss of alpha cells will be produced using 2,5-hexanedione (2,5-HD) (Pasternak, Flood, Eskin, and Merigan, 1983). I propose to establish the parameters that will optimize seeing dendritic plasticity. These parameters include the dose of 2,5-HD (amount of alpha ganglion cell loss) and the time between cessation of 2,5-HD administration and examination of dendrites (period of recovery and growth). If dendritic growth is found in this pilot project, further studies on plasticity using 2,5-HD will be proposed. For instance, I will pursue questions of the functional competence of the new dendritic material and the response of the other classes of ganglion cells to alpha ganglion cell loss.